Create a design and simulate using EE-Sim® tools: The MAX13036 contact monitor and level shifter monitors and debounces eight remote mechanical switches and asserts an interrupt (active-low INT) if a switch changes state. The state of each switch is sampled through an SPI interface by reading the status register and any switch can be prohibited from asserting an interrupt by writing to the command register. Four of the switch inputs are intended for ground-connected switches (IN0–IN3), and the other four inputs (IN4–IN7), are programmable in groups of two for either ground-connected or battery-connected switches. Two switch inputs (IN0, IN1) have direct level-shifted outputs (DO0, DO1) to be used for PWM or other timing-based signals.

Switch input thresholds are set to 50% of the voltage applied to BATREF. The threshold hysteresis is set by connecting an external resistor from HYST to ground. The MAX13036 supplies an adjustable wetting current to each closed switch to clean mechanical switch contacts that are exposed to adverse conditions.

The MAX13036 operates with a +6V to +26V battery voltage applied to BAT. A separate +2.7V to +5.5V logic supply input (VL) sets the interface voltage. The MAX13036 is available in a 5mm x 5mm 28-pin TQFN package and operates over the -40°C to +125°C temperature range.